4.4 | Droplet extrusion
The droplet suspension was extruded 30 times through 30 nm pore filters (Nuclepore Track-Etch Membrane, Whatman Inc., NY, USA) using an extruder ( Avestin Inc., Mannheim, Germany) to prepare PCNDs. The mean droplet diameter was measured using a Zetasizer Nano-ZS (Malvern Instruments Ltd., Malvern, UK).